1. Field of the Invention
The present invention relates to a system and mechanism for directing the leading edge of a continuous form onto a stack, and more particularly, to a device for appropriately directing the leading sheet(s) of a continuous form to begin a stack of forms.
2. Description of Background Information
Refolding and stacking of pre-folded continuous form paper is accomplished either by passive (gravity fed) stackers or by active stacking systems. Passive stackers may use a wire basket (or other box-shaped configuration) in combination with fixed guides. Active stackers use various devices positioned alongside the stacking platform, such as rotating paddles or air jets, to ensure that a stack of continuous form paper stacks correctly. However, laying the first few sheets of a stack is problematic with both passive and active stackers, since both kinds of stackers have no facility for appropriately placing the leading edge depending on the fold orientations encountered such that subsequent folds will develop correctly.
For example, with fan-fold continuous forms of paper or label stock, even after unfolding for printing, folds tend to remain in the continuous form in their original direction or orientation (xe2x80x9cfold memoryxe2x80x9d), alternating between outside folds and inside folds between sheets. In this context, an xe2x80x9coutsidexe2x80x9d fold is one that enters the printer with the fold cusp pointing upward, and an xe2x80x9cinsidexe2x80x9d fold is one that enters the printer with the fold cusp pointing downward. Depending where the last discrete sheet of the form is separated, a leading fold following the leading edge of the form (usually formed at a perforation between sheets) may have either of an outside or inside orientation. Accordingly, a leading fold following the leading edge has a fold cusp pointing up (xe2x80x9coutsidexe2x80x9d) or down (xe2x80x9cinsidexe2x80x9d).
If the first sheet arriving at the stacking platform arrives such that second sheet folds over in the same direction of the fold memory of the leading fold, subsequent folding of the continuous form will encounter only a small chance of misfolding. However, if the first sheet arriving at the stacking platform arrives such that second sheet folds over against the direction of the fold memory of the leading fold, then all subsequent folds will be folded against the original fold orientation or xe2x80x9cfold memory,xe2x80x9d and misfolding and mis-stacking of the continuous form media will likely occur.
Further, in a laser printer using pre-folded continuous forms, mis-stacking and misfolding often occurs when the toner-fusing or fixing rollers xe2x80x9cironxe2x80x9d out the existing folds at the perforations between sheets of the continuous form. As a result, the form folds lose a portion of xe2x80x9cfold memory,xe2x80x9d and tend not to refold easily into a stack. With high speed printers, misfolding and mis-stacking is further exacerbated.
Even when a passive or active stacker may reliably stack a continuous form when a group of initial sheets is properly laid down and folded, an operator must manually lay the first sheet. If sheet feeding is automatic, the operator must still ensure that the leading sheet is in the proper orientation for which the stacker is designed, and may be forced to remove the continuous form media, rotate the media input stack, and replace the media in the printer to orient the leading sheet properly.
Accordingly, it is an object of the invention to provide a leading edge directing system that appropriately directs leading sheets of a pre-folded continuous form so that all subsequent folding onto a stack develops correctly.
It is a further object of the invention to provide a leading edge directing system capable of directing leading sheets of a continuous form for any orientation of the folds in the pre-folded continuous form.
It is a further object of the invention to provide a fold sensor, and leading edge directing system incorporating the fold sensor, capable of detecting fold orientation in pre-folded or fanfold continuous forms.
The above objects are attained by providing a leading edge directing system for directing the leading edge of a pre-folded form to begin a folded stack in which a controller, connected to a position determining system and a motor, moves both of first and second guide members such that only one of the guide members pushes a leading edge of the pre-folded form toward a front or rear side of a stacking platform according to the position of the pre-folded form as defined by a position determining system. The guide members are movably mounted on either side of an entry path above the stacking platform through which the pre-folded form is introduced toward the stacking platform. The position determining system defines a position of the continuous form. The motor is linked to each of the guide members, and moves the guide members so that only one of the guide members may contact the continuous form at any position of the guide members.
The position determining system may include a leading edge sensor that detects a position of the leading edge of the pre-folded form relative to the guide members. In addition to the leading edge sensor, the position determining system may include a timer that measures the time taken for the leading edge of the pre-folded form to travel a predetermined distance relative to the guide members; or a form movement sensor that directly measures a distance traveled by the pre-folded form relative to the guide members; or a position input device for inputting a predetermined position of the pre-folded form relative to the guide members. Further, in addition to the leading edge system, the position determining system may include a fold orientation determining system for defining an orientation of folds in the pre-folded form, which may have a fold orientation input device for inputting a predetermined orientation of a leading fold in the pre-folded form following the leading edge; or a fold orientation sensor that detects an orientation of folds in the pre-folded form following the leading edge; or a fold position determining system for defining positions of folds in the pre-folded form relative to the guide members.
Preferably, the fold orientation sensor includes one or more walls placed along the transport path, the wall or walls forming a corner that changes a direction of the continuous form and forms a detectable clearance between a wall or walls and the continuous form. The clearance depends on predetermined stiffnesses of the continuous form and the folds. An opening is formed through the wall at the corner, and a media detection sensor, responsive to the detectable clearance to sense the folds in the continuous form, senses the continuous form at the opening.
If a fold orientation sensor is provided, it may be associated with a printer placed upstream along a form transport path leading through the entry path, where the leading edge directing system directs the leading edge of a pre-folded form output by the printer to begin a folded stack. The fold orientation sensor may be positioned upstream of the printer or within the printer along the form transport path.
In this manner, the leading edge directing system can conduct combinations of operations in which the position or orientation of the folds or leading edge are detected, set manually by an operator, or determined. The positions may be determined according to a timer from a known position, or according to direct measurement of the advance of the continuous form or the feeding device. The continuous form may also be set in a predetermined position.
The guide members may be linked to the motor by a common member to move in the same direction. In this case, the guide members may be mounted to rotatably supported shafts parallel to and on either side of to the entry path. The shafts may be driven by a common drive gear driven by the motor, and the gear ratio between the driven gears and the common drive gear may be set such that the driven gears rotate by less than a full rotation for each full rotation of the common drive gear. The common driven gear and the controller may be connected to a home position detector for detecting each full rotation of the driven gear.
The guide members may be provided with a collapsible assembly including a pin; a guide wire for pushing the leading edge of the pre-folded form toward the one of the front and rear sides of the stacking platform; and a resilient biasing member that pushes the guide wire against the pin in the same direction as the guide wire pushes the leading edge. In this manner, the guide wire is collapsible, away from the pin, when the guide wire encounters an obstacle along the same direction as the guide wire pushes the leading edge. Preferably, the collapsible assembly is rotatably mounted, and the resilient biasing member includes a torsion spring coaxial with a center of rotation of the collapsible assembly.
Preferably, each of the front and rear guide members includes one or more elongated guide wires rotatable into the entry path to push the leading edge of the pre-folded form toward the one of the front and rear sides of the stacking platform.
The motor is preferably linked to each of the first and second guide members by a transmission mechanism that maintains an angle of 30 to 100 degrees between the members at any position, so that only one of the guide members may contact the continuous form at any position of the guide members. The angle is more preferably 45 to 90 degrees, and ideally approximately 90 degrees. Below 45 degrees, and even more so below 30 degrees, during operation, there is an increased chance that the wire guide on the non-contacting side will contact or interfere with the sheet. Above 90 degrees, and even more so above 100 degrees, the mechanical design becomes cumbersome. At approximately 90 degrees, smooth operation, with each wire guide moved out of the way when not needed, is ensured.
In one modification of the system, according to the form position defined by the position determining system, the controller moves the guide members such that only one of the guide members pushes the leading edge of a first sheet of the form toward a side of the stacking platform, and subsequently moves the guide members such that the remaining guide member pushes the leading edge of the second sheet toward the remaining side of the stacking platform. In another, the controller subsequently returns the guide members to a home position in which neither guide member interferes with subsequent stacking of the continuous form.
In another aspect of the invention, a fold detector detects folds in a pre-folded continuous form moving along a transport path. The fold detector includes one or more walls placed along the transport path, the wall or walls forming a corner that changes a direction of the continuous form and forms a detectable clearance between a wall or walls and the continuous form. The clearance depends on predetermined stiffnesses of the continuous form and the folds. An opening is formed through the wall at the corner, and a media detection sensor, responsive to the detectable clearance to sense the folds in the continuous form, senses the continuous form at the opening.
In one version of this aspect of the invention, two substantially straight walls intersect to form an angled corner that changes a direction of the continuous form, so that when no detectable fold is at the angled corner, the detectable clearance forms between one of the substantially straight walls and the continuous form. When a detectable fold is at the angled corner, the detectable clearance reduces, and the media detection sensor is responsive to the reducing of the detectable clearance to sense the folds in the continuous form.
In this case, the media detection sensor may include a limit switch having a movable lever emerging from the opening at the one of the substantially straight walls, so that the movable lever is depressed and the limit switch activated when the detectable clearance is reduced. Conversely, the movable lever is released and the limit switch deactivated when the detectable clearance is formed. Preferably, the two substantially straight walls intersect at a right angle to form a right angle corner, and the wall having the opening is vertical, the remaining wall being horizontal.
In another version of this aspect of the invention, an arcuate wall forms an arcuate corner that changes a direction of the continuous form when a detectable fold is at the arcuate corner, so that the detectable clearance forms between the arcuate corner and the continuous form. When no detectable fold is at the arcuate corner, the detectable clearance is reduced, and the media detection sensor is responsive to the forming of the detectable clearance to sense the folds in the continuous form. Preferably, the arcuate wall curves from a horizontal direction to a vertical direction.
The media detection sensor may include a proximity switch directed through the opening, so that when the detectable clearance is formed, the proximity switch is deactivated, and when the detectable clearance is reduced, the proximity switch is activated.
In still another aspect of the invention, a leading edge directing system directs the leading edge of a pre-folded form (having folds formed therein) moving along a transport path to begin a folded stack. A controller, connected to a media detection sensor and a motor, moves guide members such that, depending on the positions of folds detected by the media detection sensor, the guide members push a leading edge of the pre-folded form toward one of front and rear sides of the stacking platform. The pre-folded form is introduced toward the stacking platform through an entry path above the stacking platform. The guide members are movably mounted along the entry path on either side of the stacking platform and above the stacking platform, and the motor is linked to and moves the guide members. A fold detection corner that changes a direction of the continuous form is located at a predetermined position, upstream of the entry path and along the transport path. The fold detection corner forms a detectable clearance between itself and the continuous form, and the media detection sensor is responsive to the detectable clearance to detect the positions of the folds in the continuous form.